Micro-nano bubble water process: Effect of micro-nano bubble water as mixing water on volume stability of shotcrete

As a kind of active water, micro-nano bubble water (MBW) can promote the early hydration of cement paste and improve the early mechanical strength of shotcrete. However, accelerating the hydration process of cement -based materials will increase their shrinkage deformation to a certain extent at early age. Therefore, this paper mainly studies the effect of MBW combined with aluminum sulfate alkali-free accelerator (AL) on the volume stability of cement-based materials within 180d. The results show that MBW as mixing water can reduce the autogenous and drying shrinkage of cement-based materials with AL, and also has a certain mitigation effect on water loss rate and internal humidity (IH) drop under dry conditions. It can also reduce the ring constraint shrinkage cracking time and crack width. MBW can reduce the cement paste pore size distribution of 10-50 nm, and reduce the surface tension of the aqueous solution, thereby reducing the capillary tensile stress. This paper provides some theoretical guidance for micro-nano bubble water in practical engineering applications.